Both the JT-1 and JT-2 were designs of Mr. Calvin Y. Parker who marketed the plans. The JT-1 first flew in 1968 and a few were built (N4450/N8611/N71JS are examples). The JT-2 followed in 1968 and it seems safe to assume that 100+ were completed, especially in the USA.The Freudiger SF-01 (HB-YAO) was a modified JT-1 built in Switzerland by Mr. Stefan Freudiger and completed in 1974.